Out of all the games you own or have played, which game defines you? When I say this, I mean what game tells people the type of gamer you are. For instance if you're a fan of RPG's, which RPG specifically defines you. I'm not asking what's your favorite game, I'm asking what's the biggest game which shows people your taste in games. So in the case of RPG's, if you're a retro, japanese, western, hybrid, etc fan, which game tells people "this is the type of game that I love?"
For me it's Front Mission DS. The game is an enhanced port, of a PS1 port, of a SNES game. In Japan, the SNES game sold 600,000 units, but the DS version sold a measly 50,000 Globally, with only 10,000 units for North America. This is the definition of niche game, but I adore it. It has a classic snes era RPG story, not too complex, but it's really deep. Unlike Fire Emblem, there aren't too many characters, and you regularly see them in dialogues, so they grow on you. It's also a really challenging SRPG, and pretty long too, I think I took about 35 hours to beat both campaigns. Anyway, it's a really fun SRPG, and it's cool that you can customize your unit so much, you really have to think about what body do you want (High defence, or light but allows you to carry more weapons), do you want a lot of small weapons, or a few big ones, do you want to focus in ranged combat, hand to hand, or regular close combat, what skills does each individual character have, and how can you take advantage of them, etc, etc.
Front Mission is the most in depth SRPG I have ever played. While I still prefer Fire Emblem by a bit, mostly because customizing units in Front Mission is 1/3rd the games total time, this game defines me. Only 10,000 sales in North America, and I've never met any hardcore fans of these series like me. I wish Front Mission 2, 5, and 2089 localized though, it's a shame, such a good, but underappreciated series. Heck even FM Evolved for PS3/360 was awesome.